European Biophysics Journal

, Volume 46, Issue 1, pp 59–64 | Cite as

Osmosis and thermodynamics explained by solute blocking

  • Peter Hugo NelsonEmail author
Original Article


A solute-blocking model is presented that provides a kinetic explanation of osmosis and ideal solution thermodynamics. It validates a diffusive model of osmosis that is distinct from the traditional convective flow model of osmosis. Osmotic equilibrium occurs when the fraction of water molecules in solution matches the fraction of pure water molecules that have enough energy to overcome the pressure difference. Solute-blocking also provides a kinetic explanation for why Raoult’s law and the other colligative properties depend on the mole fraction (but not the size) of the solute particles, resulting in a novel kinetic explanation for the entropy of mixing and chemical potential of ideal solutions. Some of its novel predictions have been confirmed; others can be tested experimentally or by simulation.


Osmosis Thermodynamics Kinetics Aquaporin Colligative properties Controversy 



I wish to thank Eileen Clark, Robert Hilborn, Jaqueline Lynch, Philip Schreiner, and the boys for helpful comments on an earlier draft of the manuscript. Support from the National Institutes of Health (Fellowship GM20584) and National Science Foundation (Grant No. 0836833) is gratefully acknowledged.


  1. Baierlein R (1999) Thermal physics. Cambridge University Press, New YorkCrossRefGoogle Scholar
  2. Benedek GB, Villars F (2000) Physics, with illustrative examples from medicine and biology, 2nd edn. AIP Press, New YorkCrossRefGoogle Scholar
  3. Berezhkovskii A, Hummer G (2002) Single-file transport of water molecules through a carbon nanotube. Phys Rev Lett 89:064503CrossRefPubMedGoogle Scholar
  4. Finkelstein A (1987) Water movement through lipid bilayers, pores, and plasma membranes: theory and reality. Wiley, New YorkGoogle Scholar
  5. Guell DC (1991) The physical mechanism of osmosis and osmotic pressure; a hydrodynamic theory for calculating the osmotic reflection coefficient. PhD Thesis, Massachusetts Institute of Technology, Cambridge, MAGoogle Scholar
  6. Hodgkin AL, Keynes RD (1955) The potassium permeability of a giant nerve fibre. J Physiol 128:61–88CrossRefPubMedPubMedCentralGoogle Scholar
  7. Kasahara K, Shirota M, Kinoshita K (2013) Ion concentration-dependent ion conduction mechanism of a voltage-sensitive potassium channel. PLoS One 8:e56342CrossRefPubMedPubMedCentralGoogle Scholar
  8. Kramer EM, Myers DR (2012) Five popular misconceptions about osmosis. Am J Phys 80:694–699CrossRefGoogle Scholar
  9. Kramer EM, Myers DR (2013) Osmosis is not driven by water dilution. Trends Plant Sci 18:195–197CrossRefPubMedGoogle Scholar
  10. Lea E (1963) Permeation through long narrow pores. J Theor Biol 5:102–107CrossRefPubMedGoogle Scholar
  11. Mathai JC, Mori S, Smith BL, Preston GM, Mohandas N, Collins M, van Zijl PC, Zeidel ML, Agre P (1996) Functional analysis of aquaporin-1-deficient red cells the Colton-null phenotype. J Biol Chem 271:1309–1313CrossRefPubMedGoogle Scholar
  12. Murata K, Mitsuoka K, Hirai T, Walz T, Agre P, Heymann JB, Engel A, Fujiyoshi Y (2000) Structural determinants of water permeation through aquaporin-1. Nature 407:599–605CrossRefPubMedGoogle Scholar
  13. Nelson PH (1998) Simulation of self-assembled polymer and surfactant systems. PhD Thesis, Massachusetts Institute of Technology, Cambridge, MAGoogle Scholar
  14. Nelson PH (2002) A permeation theory for single-file ion channels: corresponding occupancy states produce Michaelis-Menten behavior. J Chem Phys 117:11396–11403CrossRefGoogle Scholar
  15. Nelson PH (2011) A permeation theory for single-file ion channels: one- and two-step models. J Chem Phys 134:165102CrossRefPubMedPubMedCentralGoogle Scholar
  16. Nelson PH (2012) Teaching introductory STEM with the marble game. arXiv:1210.3641
  17. Nelson PH (2014) Osmosis, colligative properties, entropy, free energy and the chemical potential. arXiv:1409.3985
  18. Nelson PH (2015) Biophysics and physiological modeling—Chapter 5: a diffusive model of osmosis (v.4.0).
  19. Nelson PH, Auerbach SM (1999a) Modeling tracer counter-permeation through anisotropic zeolite membranes: from mean field theory to single-file diffusion. Chem Eng J 74:43–56CrossRefGoogle Scholar
  20. Nelson PH, Auerbach SM (1999b) Self-diffusion in single-file zeolite membranes is Fickian at long times. J Chem Phys 110:9235–9243CrossRefGoogle Scholar
  21. Nelson PH, Hatton TA, Rutledge GC (1999) Asymmetric growth in micelles containing oil. J Chem Phys 110:9673–9680CrossRefGoogle Scholar
  22. Panagiotopoulos AZ (1987) Direct determination of phase coexistence properties of fluids by Monte Carlo simulation in a new ensemble. Mol Phys 61:813–826CrossRefGoogle Scholar
  23. Sperelakis N (2012) Cell physiology sourcebook: essentials of membrane biophysics, 4th edn. Elsevier/AP, BostonGoogle Scholar
  24. Villegas R, Barton T, Solomon A (1958) The entrance of water into beef and dog red cells. J Gen Physiol 42:355–369CrossRefPubMedPubMedCentralGoogle Scholar
  25. Weiss TF (1996) Cellular biophysics. MIT Press, CambridgeGoogle Scholar
  26. Zhu F, Tajkhorshid E, Schulten K (2004a) Collective diffusion model for water permeation through microscopic channels. Phys Rev Lett 93:224501CrossRefPubMedGoogle Scholar
  27. Zhu F, Tajkhorshid E, Schulten K (2004b) Theory and simulation of water permeation in aquaporin-1. Biophys J 86:50–57CrossRefPubMedPubMedCentralGoogle Scholar

Copyright information

© European Biophysical Societies' Association 2016

Authors and Affiliations

  1. 1.Department of PhysicsBenedictine UniversityLisleUSA

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